Meteor scatter burst communications systems have been known and used for many years to provide for relatively inexpensive, low data rate, long distance communication of data, particularly digital data, between a master station and one or more remote stations. A basic description of a typical meteor scatter burst communications system, for example, is contained in U.S. Pat. No. 4,277,845 issued on Jul. 7, 1981 to Dale K. Smith et al.
As described therein, a master station transmits digital radio probing signals which are then reflected from the ionization trails left by meteors which have entered into and are travelling through the earth's upper atmosphere (at an altitude of about 50-70 miles above the earth's surface, for example). Such trails result from the ionization of air particles through which the meteor travels. Such ionization trails exist for only a short time interval e.g., from a few milliseconds to a few seconds, so that a signal burst transmission mode is usually used for transmitting probing signals from a master station for reflection (i.e., scattering) from the meteor trail to one or more of the remote stations and for transmitting data from a remote station by reflection from the meteor trail back to the master station.
It is found that meteor communication systems can be used to communicate over relatively long distances, e.g., up to 1000 miles, or greater, using relatively inexpensive equipment therefor. In one use of such systems, as described in the aforesaid Smith et al. patent, such systems can be used to transmit weather data from one or more remote stations to a master station. Such data may include, for example, data as to temperature, snow depth, precipitation, wind velocity, and the like, at relatively inaccessible regions where the remote stations are located.
The durations of the signal bursts, i.e., the probing signals and the return data signals, or additional signals, as discussed below, are selected so that the overall time for their transmission does not exceed the time of duration of a typical meteor trail. Thus, such bursts may normally range, for example, from tens of milliseconds to hundreds of milliseconds.
In applications where the master station transmits with relatively high power and a remote station transmits its reply with relatively low power, the remote station will be able to detect the probing signal frequently but replies will not be received by the master station as often because of the difference in the transmitting powers thereof. A further problem arises when the signal-to-noise (S/N) ratio at the remote station is not as high as is desirable, i.e., the remote station is in a radio signal "noisy" environment so that the signal transmitted from the master station cannot be readily recognized and separated from the noise which accompanies it.
A common technique for improving the performance of systems using low power transmitters is to use higher gain antennas. Such an approach, however, is often not useful for master stations used in meteor burst scatter communication systems because providing higher gain antennas at the master station means that narrower beam antennas must be used. Since it is desirable that a master station capture as many signals as possible reflected from a large number of meteor trails, it is normally desirable that relatively broad beam antennas be used thereat. If narrow beam antennas are used then many otherwise useful meteor trails would fall outside the scope of the narrow beam antenna and, accordingly, the effectiveness of the meteor scatter system would be reduced.
Accordingly, it is desirable to improve performance so as to enhance the communication between master and remote stations by devising some other technique for compensating for, or overcoming the difference in, the transmitting powers of the master and the remote stations, as well as compensating for the effects of the noise environment which may exist at the remote stations. It is desirable that such improved performance be accomplished without eliminating any potentially useful meteor trails. It is further desirable that such a technique be useful in enhancing communications not only between a master station and one or more remote stations but also between two or more master stations so as to provide greater data throughput, for example, or to provide the same data throughput with fewer errors.